1. Field of the Invention
The present invention relates to a cam mechanism, having a cam ring and used in a telescoping lens barrel (e.g., a zoom lens), for advancing and retracting a linearly movable ring by rotation of the cam ring.
2. Description of the Related Art
Miniaturization of lens barrels incorporated in optical devices such as cameras has been in increasing demand. In retractable lens barrels such as zoom lens barrels (zoom lenses) which advance and retract by rotation of a cam ring, it is desirable to reduce the length of the cam ring while securing a sufficient range of movement of each movable lens group in an optical axis direction (for example, refer to Japanese Laid-Open Patent Publication (Kokai) No. 2004-085932).